Fuse assembly for cutouts



June 24, 1958 E. H. YONKERS FUSE ASSEMBLY FOR CUTOUTS 3 Sheets-Sheet 1Filed Feb. 24, 1956 INVENTOR.

Jlme 1958 E. H. YONKERS FUSE ASSEMBLY FOR CUTOUTS 3 Sheets-Sheet 2 FiledFeb. 24, 1956 Fil Illl||ll|||ll|l| lllulllllllllllu INVENTOR.

BY M fi June 24, 1958 E. H. YONKERS 2,

FUSE ASSEMBLY FOR CUTOUTS Filed Feb. 24, 1956 3 Sheets-Sheet s UnitedStates Patent FUSE ASSEMBLY FOR coroors Edward H. Yonkers, Glencoe,Ill., assignor to Joslyn Mfg. & Supply Co., Chicago, Ill., a corporationof Illinois Application February 24, 1956, Serial No. 567,596

33 Claims. (Cl. 200-127) The present invention relates to fuse cutoutsand more particularly to an improved fuse assembly having a wide rangecurrent interrupting capacity, which may easily and quickly be mountedupon or detached from the spaced terminals of the insulator assembly.

This application is a continuation-in-part of copending application,Serial No. 344,771, filed March 26, 1953.

Recently, the trend in the design of power distribution systems has beentoward systems having higher and higher fault current capacities. Thishas created a demand for fused cutouts which are capable of interruptingvery high fault currents as well as fault currents of smallermagnitudes. Conventional cutouts of standard construction do not havethe interrupting capacity to handle the heavier fault currents.Specifically, the gas pressure built up within the fuse tube of aconventional cutout when the cutout is called upon to interruptexcessively heavy fault currents may cause splitting of the fuse tube,or the reaction from the pressure may cause fracture of the cutoutinsulator, distortion of the terminal fitting against which the reactionforce is exerted, or blow off of the fuse assembly end fitting againstwhich the reaction force is exerted. Such gas pressure build up in thefuse tube can, of course, be reduced by using larger fuse tubes havinginternal bore diameters. If this expedient is resorted to, however, theeffectiveness of the cutout in interrupting small fault currents ismaterially reduced.

'Accordingly, it is an object of the present invention to provide animproved cutout and more particularly an improved fuse assembly for usein cutouts.

It is another object of the invention to provide an improved fuseassembly for cutouts which is capable of satisfactorily interruptingfault currents over a wide range of magnitudes, including exceedinglyhigh fault currents, without damage to the fuse assembly or theinsulator assembly upon which the fuse assembly is detachably mounted.

In accordance with another and more specific object of the invention,facilities are provided for relieving the gas pressure developed in thefuse tube of a fuse assembly incident to the arc development within thetube which occurs during a circuit interrupting operation, thereby toextend the fault current interrupting capacity of the assembly.

It is still another object of the invention to provide an improved heavyfault current interrupting fuse assembly for cutouts, which may be usedinterchangeably with fuse assemblies of standard construction havinglower interrupting capacities in a cutout of given commercialconstruction.

A further object of the present invention is to pro vide a fuse assemblyfor a cutout capable of interrupting high fault currents and dischargingionized gases from one end in one direction only so as to minimize thechance of starting flash-overs associated with the cutout in normal use.

Another object of the present invention is to provide a fuse assemblyfor a cutout capable of interrupting very high fault currents having aplurality of unidirectional gas discharging passageways for relievingthe gas pressure developed within the fuse assembly incident to ordevelopment Within the tube upon interruption of very high faultcurrents.

The invention, both as to its organization and method of operation,together with further objects and advantages thereof, will best beunderstood by reference to the following specification taken inconnection with the accompanying drawings, in which:

Fig. 1 is a side view of an improved cutout including one embodiment ofa fuse assembly characterized by the features of the present invention;

Fig. 2 is an enlarged side view of the fuse assembly of Fig. 1 showingthe assembly detached from the insulator assembly of the cutout;

Fig. 3 is a sectional view taken along the lines 3-3 of Fig. 2;

Fig. 4 is a sectional view taken along the lines 44 of Fig. 2;

Fig. 5 is a sectional view of another embodiment of the fuse assembly;and

Fig. 6 is a sectional view of still another embodiment of the fuseassembly.

Referring now to the drawings, the present invention is thereillustrated in its three embodiments in an improved fuse assembly 9which forms a part of a fused cutout of the improved form disclosed andclaimed in United States Patent No. 2,493,433, granted January 3, 1950,to the present applicant. As shown in Fig. l, the insulator assembly ofthe cutout comprises a petticoat insulator 10 having a center zonelongitudinally thereof clampingly embraced by a bracket 11 which may beutilized in supporting the cutout upon a pole or another suitablesupporting structure in such position that the insulator 10 is tiltedslightly with respect to the vertical. At its respective upper and lowerends, the insulator 10 is provided with spaced apart upper and lowerterminals indicated generally at 12 and 13, respectively, and betweenwhich the fuse assembly 9 is adapted to be detachably supported.

For a description of the structural details of the upper and lowerterminals 12 and 13, reference may be had to the above identifiedpatent. Briefly, however, the upper terminal 12 extends outwardly fromthe upper end of the insulator 10 at right angles thereto and iscomprised of a conductive channel member of U-shaped cross sectionthroughout its length. At the laterally extended end thereof, theterminal member 12 is provided with downwardly extending hood skirts120, the upper portions of which are arranged in meeting engagement withan overhanging lip 12d extending downwardly from the top or base portionof the channel member 12. At their outer ends, the hood skirts 12cterminate in flared lips 12] which function to guide the upper end ofthe fuse assembly 9 within the space defined by the hood skirts 12cincident to rotation of the fuse assembly 9 to its closed circuitposition. To prevent the upper end of the fuse assembly from being movedbeyond a predetermined point longitudinally of the skirts as theassembly is swung into its closed circuit position, a stop pin 12b isprovided which extends transversely between the two identified skirts.This pin is arranged to coact with a retaining element in the form of adouble leaf spring catch member 14 to restrain the fuse tube assembly 24against drop out movement to the open circuit position thereof. At oneend, the two leaves of the spring 14 are anchored to the under side ofthe terminal member 12, by means of a terminal screw 15, which isthreaded through a re-enforced top side portion of the terminal member.Upward movement of the retaining element 14 is limited by an adjustablestop screw 14b threaded through the top wall of the terminal member 12to engage the element 14 intermediate its ends. A clamping washer 17 andnut 16 threaded onto the screw 15, may be utilized to establish linewire connections with the upper terminal member 12. a

All parts of the lower terminal 13 of the cutout are of course, made ofa conductive metal. These parts include a pair of spaced apart hingepieces 18 having elongated and aligned trunnion receiving seats 18a,formed therein, a line terminal assembly 19 and a U-shaped tensioningspring 20 having one end fixedly connected to one of the parts or" theterminal assembly 13 and the other end extending between the spacedapart hinge pieces 18. With the cutout mounted upon a suitablesupporting structure so that it occupies the intended operating positionillustrated in Fig. 1 of the drawings, the trunnion seats 18a formed inthe hinge pieces 18 are disposed in a substantially horizontal plane.

Referring now more particularly to Figs. 2, 3 and 4 of the drawings, oneembodiment of the present improved fuse assembly is there illustrated ascomprising an inner fuse tube 21 and an outer fuse tube 22 which extendbetween and are held in spaced apart relationship by upper and lowercontact members or end fittings 23 and 24, so that an annular gaspassage 37 is formed between the outer surface of the inner tube 21 andthe inner surface of the outer tube 22. The inner tube 21 is formedentirely of pressed fiber or the like, having good arc extinguishing gasevolving properties. The outer tube 22, on the other hand, comprises aninner layer also formed of pressed fiber or the like, having good areextinguishing gas evolving properties and an outer layer of Bakeliteimpregnated paper having excellent insulating and weather resistantproperties. As best shown in Fig. 3, the upper contact member or endfitting 2 3 is provided with two longitudinally spaced bores 23a and 23bfor receiving the respective upper ends of theinner and .outer tubes 21and 22. These bores are connected by an internal shoulder 230 againstwhich the upper end of the outer tube 22 abuts. A pin 38 driven intoaligned openings in the wall of the member 23 and'the outer wall of thetube 22 is utilized to maintain the parts 21, 22 and 23 in assembledrelationship. The contact member 23 is also provided with a head portion230! having an internal bore 23:: of the same diameter as the internalbore of the inner fuse tube 21 for receiving a fuse link 25. This headportion of the contact member 23 is provided with external threads forreceivingan internally threaded cap 26 which is used to close the upperend of the inner tube 21 and to hold the head 25a of the fuse link 25 inseating engagement with the top surface of the contact member headportion 23d. The cap 26 is of inverted cup-shaped configuration and hasa small compression spring 27 mounted upon the inner surface of the topwall thereof which is utilized to press the head 25a of the fuse link 25into seating engagement with the top end of the contact member 23 as thecap 26 is threaded onto'the head portion 23:! of the contact member 23.

At their lower ends, the tubes 21 and 22 are supported by the lowercontact member or end fitting 24 which includes a laterally extendingand conductive supporting arm 28. More specifically, and as best shownin Fig. 3, the lower contact member 24 is provided with longitudinallyspaced bores 24a and 24b for respectively re ceiving the lower ends ofthe fuse tubes 21 and 22. These bores are connected 'by an internalshoulder'24c against which the lower end of the tube 22 abuts. 7 setscrew 39 threadedly received within an opening in the wall of the member24 engages the outer wall of the tube 22 to maintain the parts 21, 22and 24 in assembled relationship. For the purpose of venting the annulargas passage37 to the atmosphere, vent ports or openings 29 are drilledthrough the lower Wall of the member 24 at several points around thecircumference "4' thereof in the manner best shown in Figs. 3 and 4 ofthe drawings. i

The laterally extending and conductive supporting arm 28 is of invertedT-shaped cross section throughout the major portion of its length. Atits extended end, the arm 28 is forked to provide spaced apart endpieces 30 having oppositely directed trunnions 31 projecting outwardlytherefrom which are receivable within the slotted hinge pieces 18 of theinsulator assembly to seat upon the trunnion seats 18a. Between thetransversely spaced end pieces 33 of the arm 28, there is supported afuse pigtail extracting arm 32. More specifically, the pivoted end ofthe arm 32 is fixedly connected to a pivot pin 33 which is journaled inaligned openings in the trunnions 31. The main part of the arm 32 isbent into the configuration shown in Fig. 2 of the drawings to haveparallel extending intermediate and return bent portions 32a and 3211, aloop shaped end bridge 32c and a. camming portion 32d which isengageable with the free end of the spring 29 as the fuse assembly 9 isrotated into its closed circuit position after the trunnions 31 areengaged with the trunnion seats 18a of the hinge pieces 18. A brace .40connected between the pin 33 and the arm 32 in the manner illustrated inFig. 2 is provided to prevent distortion of the shape of the cammingportion 32d of the arm 32. Intermediate the ends of the arm 32, meanscomprising a headed tie post 34 are provided for securely connecting thepigtail conductor 25b of the fuse link 25 to the arm 32. Specifically,the post 34 is fixedly mounted upon the intermediate portion 32a of thearm 32 and extends downwardly through a slot opening in the return bentportion 321) of the arm. At its extended end, the post 34 fixedlysupports a curved pigtail retaining head 35, which in cooperation withthe arm portion 32b serves fixedly to connect the pigtail conductor 25bto the arm 32.

In. order to provide for switch stick manipulation of the hingedtrunnions 31 into engagement with the trunnion seats of the hinge pieces18, the upstanding center part of the T-shaped supporting arm 28 isenlarged at a point adjacent the forked outer end of the arm to providefor the formation of an opening 28a therein into which the hook of aswitch stick may be inserted. Similarly, the upper contact member 23 ofthe fuse assembly 9 is provided with an integrally formed loop portion23 into which the hook of a switch stick may be readily inserted topermit use of a switch stick in swinging the fuse tube assembly into andout of its closed circuit position.

From the above explanation, it will be apparent that when ,the fuseassembly is detached from the terminals 12 and13of the insulatorassembly, the supporting arm 28 and the extracting-arm 32 are freelyrotatable relative to each other. When it is desired to fuse theassembly 9, the terminal cap 26 is unscrewed from the head portion 23dof the contact member 23 and a fuse link 25 inserted within the chamberor bore of the inner fuse tube 21 so that the pigtail conductor 25bthereof projects out of the open lower end of the tube 21. Followingthis operation, and with the extracting arm 32 firmly held against thesupporting arm 23, the projecting part of the conductor 25b is carriedover the bridge portion 320 of this arm and wrapped around the post 34beneath the head 35 while the arm portion 32b is depressed onto the headportion 23;! of the upper contact member 23 until the cap rim abuts theupper shoulder of the contact member head portion 23d, thereby toestablish the exact desired distance between the top of the cap and theaxis of the trunnions 31. As the cap 26 is screwed onto the head portion23d of the upper contact member 23, the spring 27 is compressed to clampthe head 25a of the fuse link tightly against the upper end of thecontact member 23.

A switch stick having its hook engaged with the opening 28a of the arm28 may be utilized to engage the trunnions 31 of the fuse assembly 9with the trunnion seats 18a of the hinge pieces 18 in assembling thefuse assembly 9 upon the insulator assembly. Likewise, the hook of theswitch stick may be engaged with the loop portion 231 of the uppercontact member 23 for the purpose of rotating the use assembly into itsclosed circuit position. As the fuse assembly 9 is rotated in a counterclockwise direction to its closed circuit position, the free end of thebiasing spring 20 rides up the camming portion 32d of the extracting arm32 and in so doing reacts between the extracting arm 32 and its supportto perform three functions. First, it forces the trunnions 31 forwardalong the seats 18a toward the noses of the hinge pieces 18, thereby toposition the end cap 26 for interlocking engagement with the retainingspring 14. Secondly, it biases the bridge portion 320 of the extractingarm 32 away from the supporting arm 28 to tension the pigtail conductor25b and hence, the fusible element within the fuse link 25. Thirdly, itfunctions to force the trunnions 31 into pressure engagement with theforward ends of the trunnion seats 18a, thereby accurately to center theupper end of the fuse assembly 9 relative to the front or entranceopening between the lips 12] of the upper terminal member 12. As the endcap 26 moves between the lips 12f and the skirts 12c of the upperterminal member 12, it engages and rides beneath a catch portion 14a ofthe retaining spring 14 until it is brought to bear against the stop pin12b. As the end cap 26 is moved into engagement with the stop pin 12b,the lip 14a of the retaining spring 14 drops over the edge of the cap 26to latch the assembly 9 in its closed circuit position. With the fuseassembly 9 in this position, a fused current path is provided betweenthe terminals 12 and 13 which extends from the terminal member 12 by wayof the retaining spring 14, the contact member 23, the fusible elementof the link 25, the pigtail conductor 2512, the extracting arm 32 to theterminal assembly 13.

So long as current flow over the described conductive path between theterminals 12 and 13 does not exceed the rated current carrying capacityof the link 25, the fusible element within the link 25 servesmechanically to hold the extracting arm 32 in its set position againstthe underside of the supporting arm 28. When, however, this fusibleelement is subjected to a fault current, such that it is called upon tocarry current in excess of its rated capacity, it is ruptured to relievethe holding force imposed upon the extracting arm 32 through the pigtailconductor 25b. As a consequence, the spring 20, in reacting between thesupporting insulator and the camming portion 32d of the arm 32 functionsrapidly to rotate the arm 32 downwardly about the pivot pin 33 therebyto withdraw the pigtail conductor 25a from the lower end of the fusetube 25. As the arm 32 is rotated to a position approximately normal tothe supporting arm 28, the camming portion 32d thereof tends to moveaway from the spring 20 thus relieving the force holding the trunnions31 at the forward ends of the trunnion seats 18a. As this force isrelieved, the retaining spring 14 in thrusting downward upon the end cap26 combines with gravity pull on the assembly 9 to slide the trunnions31 to the left along the trunnion seats 18a. As a result, the distancebetween the trunnions 31 and the retaining spring 14 is increased untila point is reached where the catch 14a no longer engages the side '6 ofthe end cap 26'. Thus, the fuse assembly 9 is released for downwardpivotal drop out motion about the axis of the trunnions 31 under theinfluence of gravity pull on the assembly.

As will be understood by those skilled in the art, incident to ruptureof the fusible element within the link 25 an arc is developed betweenthe upper end of the pigtail conductor 25b and the remnant of thefusible element within the fuse link 25, which is rapidly elongated asthe pigtail conductor 25b is withdrawn from the bore of the inner fusetube 21 under the influence of the extracting arm 32. This aredevelopment within the inner fuse tube 21 results in contacting of thearc with the inner walls of the fuse tube with the result that the arcis cooled and arc extinguishing gases are released from the inner wallsof the tube 21. The heat gener: ated by the confined are also results inan extremely rapid rise in the gas pressure within the tube 21, whichhas the effect of blowing the are out as the gases are rapidly expelledfrom the lower end of the tube. The extent of the temperature risewithin the tube 21 and hence the extent of the pressure rise within thetube increases as a function of the magnitude of the fault current beinginterrupted. In other words, the heavier the fault current the greaterthe gas pressure built up within the tube 21. This rise in gas pressureis, of course, desirable since it results in rapid expulsion of ionizedparticles from the lower end of the tube and hence, enhances therapidity of arc extinction. However, expulsion of the gases from thelower end of the tube 21 obviously sets up reaction forces which areexerted through the end cap 26 against the outer end of the elongatedupper terminal member 12. It has been found that when a standard singletube fuse assembly is called upon to interrupt fault currents of theorder of 5,000 amperes, for example, the gas pressures developed in thefuse tube become high enough to cause splitting of the fuse tube, or todevelop reaction forces which may result in distortion of the upperterminal member 12, blowing oil. of the end fitting 23, or fracturing ofthe insulator 10.

In order to obviate the problems outlined in the preceding paragraph,the double tube arrangement comprising the inner and outer tubes 21 and22 is provided so that two gas expulsion passages are formed, namely thegas expulsion passage within the inner tube 21 and the annular passage37 between the two tubes 21 and 22.

These two passages are both vented to the atmosphere at the same end ofthe assembly 9 and are in gas flow communication with each other throughvent openings 36 drilled through the walls of the tube 21 at pointsintermediate the ends of the tubes 21 and 22. More specifically, fivesets of aligned vent ports 36 are provided through the wall of the tube25 in the region of maximum gas pressure development within the tubeduring a circuit interrupting operation of the cutout. The sets of ports36 are equally spaced around the tube 21 and each port extendsdownwardly from the inner surface of the tube to the outer surfacethereof at an angle of approximately 45 relative to the tube wall.

With the described dual gas passage arrangement, a portion of the hotarc extinguishing gases generated during a fault current interruptingoperation pass from the central gas discharge passage within the tube 21through the vent ports 36 to the passage 37 and are discharged to theatmosphere through the vent ports 29. As a consequence, the reactionforce exerted against the end fitting 23 and the end of the terminalmember 12 are substantially reduced to a value which will not cause blowoff of the end fitting or damage to the terminal member 12 or theinsulator 10. In addition, the gases are cooled to aid in deionizationthereof as they pass through the ports 36 into the passage 37. Moreover,in passing into the passage 37 the gases develop a pressure within thispassage against the outer walls of the inner tube 21 which opposes thepressure being exerted against the inner walls of the tube 21 by thegases remaining in this tube. As a consequence, the pressure load on theinner. tube 21 and hence, the tube bursting forces are materiallyreduced. It has been found, for example, that when a fuse assentbly 9 ofthe improved form illustrated in Figs. 2, 3, and 4, is substituted for astandard single tube fuse assembly in a cutout of the improvedconstruction illustrated in Fig. l, the cutout is easily capable ofinterrupting fault currents in excess of 10,000 amperes without anyapparent dam.- age either to the fuse assembly or the insulatorassembly.

Oneof the important features of this embodiment of the inventionpertains to the relative dimensioning of the ports 36 and the outer gaspassage 37. Thus, if the total cross sectional area of the ports 36 andthe cross sectional area .of the passage 37 are too large, such thatgases may easily flow from the inner gas passage within the tube 22 tothe passage 37, the interrupting ability of the fuse assembly on faultcurrents of small magnitude is substantially impaired. This is true forthe reason that the larger overall gas discharge capacity of the twopassages mitigates against the are coming in contact with the walls ofthe tubes 21 and 22 and also against desired rapid expulsion of theionized gases from the passages. It is isportant, therefore, tosoproportion the dimensions of the ports 36 and the'passage 37 that thedesired pressure relief is obtained when the fuse assembly is calledupon to interrupt very large fault currents, without impairing to toogreat a degree the gas pressure build up which occurs within the innerpassage when the fuse assembly 9 is called upon to interrupt faultcurrents of smaller mag nitude. It has been found experimentally thatthese two requirements'are satisfactorily met'by maintaining the totalcross sectional area of the ports 36 less than the cross sectional areaof the outer passage 37 and less than the cross sectionalarea of theinner passage within the tube 21. By way of specific example, it hasbeen found that satisfactory fault current interruption over a widerange of fault current magnitudes is obtained by employing a fusestructure in which the total cross sectional area of the ports 36 is.136 square inch, the cross sectional area of the gas passage in theinner tube 21 is .150 square inch, the cross sectional area of the outergas passage 37 is .172 square inch and the total cross sectional area ofthe vent ports is equal to the sum of the cross sectional areas of thetwo passages, or .322 square inch.

- In accordance withother aspects of the present invention, and as bestshown in Figs. and 6, thetubes in the fuse' assembly may be increased innumber and fixedly secured between the upper and lower contact membersby improved means other than described above with reference to the firstembodiment. in the second embodiment of the present invention shown inFig. 5, inner and outer tubes 5% and 51, respectively, are disposedbetween upper and lower contact members 52 and 53, respectively, whichare generally similar in design and function to the upper and lowercontact members 23 and 24 of the first embodiment. The lower contactmember 53 is not secured to both of the tubes 56 and 51, but only to theouter tube 51. More specifically, the inner tube 55 is fixedly securedsolely to the upper contact member 52 in such a manner as rigidly andfreely to suspend the inner tube 50 concentrically within the outer tubeand the lower contact member, thereby to define an annular gas dischargepassageway 58 between the tubes 5i) and 51 in addition to the gasdischarge passageway 55 de fined by the bored the tubeSil. Inparticular, the upper contact'member 52, is provided with twolongitudinally a above.

horizontal portion 52 The contact member 52 is pro-j vided with anexternally threaded portion 52g for engagement with a cap like thatshown at 26 in Fig. 3. This cap effectively covers the upper end of thecontact 52 and closes the gas passageway 59 formed within tube 50.

The ends of the hollow tubes 5t? and 51 are adapted to be seated againstthe ends of the bores 52a and 52b and are maintained in assembledrelationship with the contact member 52 by means of pins 54 driven intoaligned openings in the walls of the members 52, 51 and St) in themanner shown. The inner and outer tubes 50 and 51 are retained inaligned spaced relationship by a sleeve 55 encircling the tube 50 andhaving its upper end abutted against the horizontal portion 52] of theconnecting shoulder 520. The sleeve 55 is provided with radiallyextending apertures for accommodatingthe pins 54 in order to hold thesleeve in assembly with the'tubes 5G and 51. In addition to thefastening action afforded by the pins 54, the outer tube 51 is rigidlysecured to the upper contact member by means of a suitable bondingmaterial 56, preferably an epoxide resin activated by a catalyzer agent,which occupies the space between the outer surface of the tube Sit andthe inner surface of the contact member 52 along the longitudinalabutting annular areas thereof. If an epoxide resin is used as thebonding material and this resin is activated in situ with a catalyzer, asolid Weld fusing the outer tube 51 to the upper contact member 52 isobtained within an hour after the resin 'is catalyzed. The sameprocedure and bonding agent is used to bond the sleeve 55 to the innersurface of the outer tube 51 and to affix the upper end of the sleeve tothe contact member 52. The use of two attaching means in the mannerdescribed insures that the upper contact portion of the fuse assemblywill not blow off during rated operation of the assembly. i

As in the first embodiment of the invention, the inner tube 50 isprovided with a set of equally spaced radially inclined ports 57. Theports, inclined at approximately 45 in the inner tube 5%, cause anupward thrust on the tube so that under the severest operatingconditions it is easily retained in place by the mounting meansdescribed 'As shown, the lower end of the inner tube 50 is terminatedinside of the outer tube 51 in a manner such that the gas dischargepassageway 58 is vented directly to the atmosphere. This arrangement ishighly desirable inasmuch as a fully open gas discharge passageway 58 isprovided which is entirely free from any structural element that mightimpede the expulsion of the gases generated within the fuse assemblyduring operation thereof. For the reasons stated above, the lower end ofthe inner tube 50 is not attached to the lower contact member 53. Thelower cont act member 53 is, however, rigidly attached to the outertubeSl along substantially the entire longitudinal inner surface of themember 53 by means of a bonding material like that employed with theupper contact 52, which material fuses the member 5'3 and the tube 51together as indicated at 60. In general, the overall dimensions of theindividual tubes 50 and 51, the ports defined in the inner tube 5t andthe gas discharging passageways are substantially identical to thedimensions of the corresponding components of the first embodiment ofthe fuse assembly shown in Fig. 3, with one exception. In order tofacilitate expulsion of generated gases and to reduce the pressurebuild-up within the fuse assembly, the longitudinal internal bores ineither or both of the tubes 5% and '51 may be tapered in such a manneras to provide downwardly diverging gas discharge passageways. As anexample, in a 78 kv. fuse assembly rated to carry 100 amperescontinuously with a 10,000 ampere interrupting ability, the longitudinalbore in the inner tube '56 has an internal diameter of 7/ at its upperend tapering outwardly to at the bottom. In addition to relievinggenerated gas pressures incident to arc development within the fuseassembly, the tapered bore in the tube 50 aids the escape of fuse linkcomponents which must be ejected ahead of the gases. Moreover, thelarger diameter at the bottom of the bore in the tube 51 permits theexpansion of the tubes as a result of moisture entering their exposedlower ends, thereby preventing the blocking of the annular gaspassageway 58. While the entire length of the bore in the tube 51 hasbeen illustrated as being tapered, in some cases it may be desirable totaper only the lower portion of the tube to provide the beneficialresults described above.

In accordance with the third embodiment of the present invention, shownin Fig. 6, there is provided a fuse assembly having three concentrictubes disposed between the upper and lower contact members, in contrastto the two concentric tubes of the first and second embodiments. Thesetube 62, 63 and 64, like the tubes 21 and 22 of the first embodiment areformed entirely of pressed fibre or the like, having good arcextinguishing gas evolving properties. As is well known in the art,whenever cutouts are required to operate at higher voltages, the gaspressures generated within the fuse assemblies during an interruptionincrease accordingly. To effectively decrease these resulting highpressures, three concentric tubes, namely the inner tube 62, theintermediate tube 63 and the outer tube 64, are disposed between upperand lower contact members 75 and 76. The inner tube 62 and theintermediate tube 63 are each provided with radially disposed gasdischarge ports 65 and 66 inclined at approximately 45 and extendinggenerally downward from the interior of each tube to its exterior. Theset of ports 65 and 66 are each disposed in rows which are staggeredwith respect to each other. In this manner, three gas dischargepassageways 67, 68 and 69 are defined, the first passageway 67 beingdefined by the longitudinal bore of the inner tube 62, the secondpassageway 68 being defined by the annular air gap between the innertube 62 and the intermediate tube 63 and communicating with the innerbore 67 through the gas discharge ports 65, and the third passageway 69being defined by the annular air gap between the intermediate tube 63and the outer tube 64 and communicating with the second gas dischargepassageway 68 through the gas discharge ports 66. As is evident from acomparison of Figs. 5 and 6, the radial ports defined in the tubes havea somewhat larger cross sectional area than the corresponding radialports defined in the tubes of the embodiment shown in Fig. 5, but,nonetheless, the total of the cross sectional area of each set of radialports is less than the cross sectional area of the gas dischargingpassageways 68 and 69. As indicated hereinbefore, it is important toretain this relationship of area to obtain the desired pressure reliefwhen the fuse assembly is called upon to interrupt very large faultcurrents without impairing the gas pressure build-up which occurs withinthe inner gas discharging passageway when the fuse assembly interruptsfault currents of smaller magnitude.

Since the radial ports 65 and 66 create and maintain an upward thrustfor urging the inner tube 62 and the intermediate tube 63 against theupper contact 75, it is possible to provide the long unimpeded gaspassages required for the higher voltages without having to resort toheavy expensive mounting structures. It should be understood that in theoperation of an expulsion current interrupter it is not necessary toexpel all the ionized gases, but only necessary to deionize the gaseswhich remain in the space between the elements of the currentcarryingcircuit which are separated to initiate interruption of the current.This so-called expulsion interruption is only applicable to alternatingcurrent since the deionization process requires a momentary cessation ofthe ion producing effect of arc current and voltage. In other words,when the alternating fault current passes through zero (120 times persecond in the case of cycle power current) the ions which comprise thearc-path commence to recombine into insulating gas molecules at a highrate of speed. The speed of recombination is a function of temperatureand proximity of non-ionized matter of any kind. Hence, if the arc isextended in a fibre tube, the heat of the arc releases unionized watervapor which has a momentum elfect continuing during the passage throughcurrent zero, thereby diluting the ionized gases and speeding up theirrecombination, and at the same time increasing pressure within the tubewhich causes the expulsion of both ionized and non-ionized gases.

Accordingly, the extended fibre surfaces of the tubes 62, 63 and 64accelerate the above-mentioned processes and, in addition, reducepressures in the neighborhood of the arc by permitting expansion andcooling as the generated gases are permitted to pass into the second andthird gas discharge passageways 68 and 69, through the ports 65 and 66,respectively. The structure of this fuse assembly effectively cushionsor reduces substantially the sharp upward thrust encountered in theconventional single vent fuse tube where all of the generated gases areejected through the single tube at extremely high velocity.

In the embodiment of the fuse assembly shown in Fig. 6, the three tubes62, 63 and 64 are inserted into a cavity 60a of the upper contact member75 and are maintained in assembled and abutting relationship withrespect to the upper contact by means of pins 72 driven through alignedopenings in the walls of the upper contact member 75 and the tubes 62,63 and 64. Specifically, the upper ends of tubes 63 and 64 abut againsta horizontal shoulder 75a in the contact 75 while the tube 62 has itsupper end seated within an appropriately shaped groove 75b offsetsomewhat from the shoulder 75a. In order to maintain the tubes 62, 63and 64 in spaced, concentric relationship, there are provided sleeves 70and 71 respectively disposed between the tubes 62 and 63 and between thetubes 63 and 64. The upper and lower contact members 75 and 76 are fusedto the outer tube 64 as indicated in Fig. 6 at 73 and 74, respectively,by means of a suitable bonding material of the type described above. Inaddition, bonding material is employed to seal the sleeve 70 to the tube63 and to seal the sleeve 71 to the tube 64. Consequently, the tubes 62and 63 are suspended from the upper contact 75 with their lower endsspaced from the lower contact member 76. The three tubes are of suchlength that they terminate in tiered relationship wherein tube 62terminates within the tube 63 and the tube 63 in turn terminates withinthe tube 64.

In order to relieve the gas pressure build-up within the fuse assemblyand to assist the ejection of the combustible fuse link components aheadof the ionized and nonionized gases, the longitudinal bores of the tubes62, 63 and 64 are preferably tapered in such manner that a plurality ofdownwardly diverging gas discharging passageways are provided. Theenlarged diameters of the lower ends of the bores in the tubes againprevents moisture induced expansion or the like from blocking orobstructing the gas discharge passages. Again, it should be recognizedthat, while the entire lengths of each of the bores is illustrated asbeing tapered, in some cases it may be desirable to taper only the lowerportion of the bore in each of the tubes 63 and 64. Manifestly, the setsof communicating ports reduce the pressure in the region of the faultcurrent are by permitting expansion and cooling of the generated gasesthrough the communicating ports into the multiple discharging passages,thereby relieving pressures in the fuse assembly which might otherwisereach destructive levels before the inner tube is cleared of partiallycombustible fuse linkage.

It will be readily appreciated that there has been provided in theembodiment of the invention shown in Fig. 6 a plurality of individuallyvented gas discharging passages to enable the fuse assembly to operateat much higher voltages without requiring heavy and expensive highpressure structures. Moreover, it has been deter- 11 mined that the fuseassembly incorporating the features described above is practicallyindestructive even though it is functioning to interrupt high faultcurrents While difi'erent embodiments of the present invention have beendescribed, it Will be understood that various modifications may be madetherein which are within the true spirit and scope of the invention asdefined in the appended claims. a

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A fuse assembly for cutouts, comprising a pair of spaced contactmembers engageable with the terminal members of the cutout, and astructure of dielectric material supported between said contact members,said structure including parts formed of gas evolving material definingtwo elongated and concentrically arranged gas discharge passages both ofwhich are closed at one end of the assembly and are vented to theatmosphere at the other end of the assembly, and having a plurality ofinterconnecting ports therebetween at points intermediate'the endsthereof for transmitting gas evolved upon arc development in the innerone of said passages from said one passage'to the outer one of saidpassages, the total crosssectional area of said ports being less thanthe crosssectional area of the outer one of said passages.

2. The fuse assembly of claim 1 wherein said structure comprises a pairof tubes arranged one within the other and at least the innerof which isformed of gas evolving material, wherein said contact members are eachprovided with longitudinally spaced bores of different diameters forreceiving the respective upper and lower ends of said tubes to hold saidtubes concentrically one within the other so that a gas dischargepassage is formed therebetween, and wherein one of said members isprovided with at least one opening therethrough for venting said passageto the atmosphere.

3. The fuse assembly defined by claim 2 wherein upper and lower contactmembers are provided each having longitudinally spaced bores ofdifferent diameters for receiving the respective upper and lower ends ofsaid tubes, the upper of said contact members being provided with aninternal shoulder extending between the longitudinally spaced bores ofsaid upper contact member which closes the upper end of the gasdischarge passage and the lower of said contact members being providedwith openings therethrough for venting said passage to the atmosphere.

4. A fuse assembly for cutouts, comprising a pair of spaced contactmembers engageable with the terminal members of the cutout, and astructure of dielectricma- I terial supported between said contactmembers, said structure including concentric tubes formed of gasevolving material, means carried by at least one of said contact membersfor fixedly spacing apart said tubes, there by defining a plurality ofconcentric gas discharge passages, means adjacent to the other of saidcontact members for individually venting each of said discharge passagesdirectly to the atmosphere, and means in at least one of said tubesdefining a plurality of ports interconnecting said passages fortransmitting gas evolved upon arc development within one of saidpassages from said one passage to another of said pass-ages.

l 5. A fuse assembly for cutouts, comprising a pair of spaced contactmembers engageable with the terminal members of the cutout, and astructure of dielectric mate? rial supported between said contactmembers, said struc-. ture including parts formed of gas evolvingmaterial defining two elongated and concentrically arranged gasdischarge passages both of which are closed at one end of the assemblyand are individually vented to the atmosphere at the other end of theassembly, and having a plurality of interconnecting ports therebetweenat points intermediate the endsthereof for transmitting gas evolved uponarc development in the inner one of said passages from saidone passageto the outer one of said passages,

6. A fuse assembly for cutouts, comprising a pair of spaced contactmembers engageable with the terminal members of the cutout, and astructure of dielectric material supported between said contact members,said struc-' ture including parts formed of gas evolving materialdefining two elongated and concentrically arranged gas dischargepassages, means for individually and directly venting'one end of each ofsaid passages to the atmosphere, said structure having a plurality ofinterconnecting ports between said passages at points intermediate theends thereof for transmitting gas evolved upon arc development in theinner one of said passages from said one passage to the outer one ofsaid passages.

7. The structure defined by claim 6 wherein the total cross-sectionalarea of said ports is less than the crosssectional area of the outer oneof said passages.

' 8.'A fuse assembly for cutouts, comprising a pair of tubes arrangedone within the other and at least the inner of which is formed of gasevolving material and defines a first gas discharge passageway, upperand lower contact members engageable with the terminal members of thecutout, means for securing both of said tubes to the upper contactmember in spaced apartrelationship in order to hold said tubesconcentrically one within the other, thereby forming a second gasdischarge passage therebetwe'en, means at the lower end of said tubesfor individually venting said passages to the atmosphere, and the innerof said tubes having a plurality of ports through the wall thereof atpoints spaced intermediate the ends of said tube for transmitting gasevolved upon arc development within said first passage to said secondpassage.

9. The fuse assembly of claim 1 wherein said structure comprises a pairof tubes arranged one within the other and at least the inner ofwhich isformed of gas evolving material, means for securing both of said tubesto the upper contact member in spaced apartrelationship in order to holdsaid tubes concentrically one within the other, and means in said lowercontact member for separately venting the lower end of each of saidpassageways directly to theatmosphere. I

10. A fuse assembly for cutouts, comprising a pair of tubes arranged onewithin the other and at least the inner of which is formed of gasevolving material, upper and lower contact members engageable with theterminal members of the cutout, and means securing each of said tubes tothe upper contact member in spaced apart relationship in order to holdsaid tubes concentrically one within the other so that a gas dischargepassage is formed therebetween, the upper of said contact members beingprovided with structure abutting the upper end of said inner-tube, theinner of said tubes having a plurality of ports through the wall thereofat points intermediate the ends of said inner tube for transmitting gasevolved'upon arc development within said inner tube to said passage,said ports being inclined downwardly from the interior to the e xteriorof the inner tube so that the gas flow therethrough produces an upwardthrust urging the inner tube against said structure.

11. The structure defined by claim 10 wherein the total cross-sectionalarea of said ports is less than the crosssectional area of said gaspassage.

12. A fuse assembly for cutouts comprising a pair of tubes arranged onewithin'the other and at least the inner of which is formed of gasevolving material and provides a first gas discharge passageway, upperand lower con tact members engageable with the terminal members of thecutout, and means securing each of said tubes to the upper contactmember in spaced apart relationship in order to hold said tubesconcentrically one within the other so that a second gas dischargepassageway is formed therebetween, the lower end of each of said passageways being vented directly to atmosphere, the upper of said contactmembers being provided with'structure abutting the upper end of saidinner tube, the inner of said tubes having a plurality of ports throughthe wall thereof at points intermediate the ends of said inner tube fortransmitting gas evolved upon arc development within said inner tube tosaid second passage, said ports being inclined downwardly from theinterior to the exterior of the inner tube so that the gas flowtherethrough produces an upward thrust urging the inner tube againstsaid structure.

13. The structure defined by claim 12 wherein the total cross-sectionalarea of said ports is less than the cross-sectional area of the secondpassage.

14. A fuse assembly for cutouts comprising a pair of tubes arranged onewithin the other and at least the inner of which is formed of gasevolving material, upper and lower contact members engageable with theterminal members of the cutout, and means for securing each of saidtubes to the upper contact member in spaced apart relationshipin orderto hold said tubes concentrically one within the other so that a gasdischarge passage is formed therebetween, the inner of said tubes havinga plurality of ports through the wall thereof at points intermediate theends of said tube for transmitting gas evolved upon arc developmentwithin said inner tube to said passage, said ports being inclineddownwardly from the interior to the exterior of the inner tube so thatthe gas fiow therethrough produces an upward thrust urging the innertube against said upper contact member.

15. A fuse assembly for cutouts, comprising a pair of tubes arranged onewithin the other and at least the inner of which is formed of gasevolving material, and upper and lower contact members engageable withthe terminal members of the cutout and each secured to the outer tube,the upper contact member being provided with longitudinally spaced boresof different diameters for respectively receiving the upper end of theinner and outer tubes to hold said tubes concentrically one within theother so that a gas discharge passage is formed therebetween, said uppercontact member being provided with a first internal shoulder extendingbetween the longitudinally spaced bores of said upper contact member forabutting the upper end of said outer tube and a second internal shoulderin abutting relationship with the upper end of the inner tube, the innerof said tubes having a plurality of ports through the wall thereof atpoints intermediate the ends of said tubes for transmitting gas evolvedupon arc development with said inner tube to said passage, said portsbeing inclined downwardly from the interior to the exterior of saidinner tube so that gas flowing therethrough produces an upward thrustdirecting said inner tube against said second shoulder.

16. The structure defined by claim 15 wherein the total cross-sectionalarea of said ports is less than the crosssectional area of said passage.

17. The fuse assembly of claim 1 wherein said structure includes atleast three concentric tubes of gas evolving material definingconcentrically arranged gas discharge passages.

18. The fuse assembly of claim 17 wherein said three concentricallyarranged fuse tubes are secured to said contact members in spaced apartrelationship, and wherein, each of said discharge passages areindividually and directly vented to atmosphere.

19. The fuse assembly of claim 18 wherein one end of each of said fusetubes is fixedly secured to and in engagement with one of said contactmembers to close one end of each of said gas discharge passages and theevolved gas is vented to the atmosphere at the other end of each of saidgas discharge passages.

20. The fuse assembly of claim 18 wherein said fuse tubes are sodimensioned that each of the gas discharge passages has a progressivelyincreasing cross-sectional area toward its vented end for facilitatingexpulsion of evolved gases within said fuse assembly.

21. The fuse assembly of claim 18 wherein said interconnecting ports areinclined downwardly from the inte- 14 rim to the exterior of the tube inwhich they are formed.

22. The fuse assembly of claim 21 wherein the interconnecting ports ineach tube are inclined at approximately 45 and are disposed inlongitudinal rows, the ports in one tube being staggered with respect tothe ports in an adjacent tube.

23. In a fuse assembly for cutouts of the type including spaced contactmembers engageable with the terminal members of said cutout, an outerdielectric member fixedly interconnected between said spaced contactmembers, at least one inner dielectric member disposed within andconcentrically of said outer member to define therebetween a gasdischarge passage; means for securing both said inner and outer membersto one of said contact members in spaced apart relationship so that aninner member is freely suspended and has a free end spaced from saidouter dielectric member in order to vent said gas discharge passage andpermit escape of gas evolved within said fuse assembly.

24. A fuse assembly for cutouts, comprising a pair of spaced contactmembers engageable with the terminal members of the cutout, and astructure of dielectric material including inner and outer fuse tubes atleast the inner of which is formed of gas evolving material, the outertube being engageable with both of said spaced contact members and theinner tube being attached to only one of said contact members and beingfreely suspended with its free end spaced from said outer tube, meansfor maintaining said tubes in concentric spaced relationship, said innerand outer tubes defining therebetween a gas discharging passage ventedto the atmosphere at the end thereof adjacent to the free end of saidinner tube, said inner tube having defined therein at least oneinterconnecting port for transmitting gas evolved upon arc developmentin said fuse assembly to said gas discharging passage.

25. The fuse assembly of claim 24 wherein said port is inclined towardthe vented end of said passage from the interior to the exterior of theinner tube.

26. The fuse assembly of claim 24 wherein said di electric members areso dimensioned that said gas passage has a greater cross-sectional areaat its vented end.

27. A fuse assembly for cutouts, comprising a plurality of tubestelescopically arranged and at least the inner of which is formed of gasevolving material, an upper contact member provided with longitudinalbores of different diameters for receiving the upper ends of said tubes,a lower contact member having a bore for receiving therein the lower endof the outermost of said tubes, means for fixedly securing said tubes tosaid upper contact member in spaced apart concentric relationship suchthat gas discharging passages are defined by said tubes each having oneend directly vented to the atmosphere at a point adjacent said lowercontact, each tube with the exception of the outermost tube havingdefined therein ports for interconnecting said passages to permit flowof evolved gas, each tube except the outermost tube being freelysuspended from said upper contact member and having free ends spacedapart to directly vent each of said passages to the atmosphere.

28. The fuse assembly of claim 27 wherein said ports are inclined towardthe vented end of said passage from the interior to the exterior of theinner tube.

29. The fuse assembly of claim 4 wherein the outer of said tubes issupported from both of said contact members and an inner tube issuspended from only one of said contact members and is spaced from theother of said contact members.

30. The fuse assembly of claim 4 wherein said structure includes anouter and an inner tube which cooperate to define outer and inner gasdischarge passages, said ports being defined in said inner tube only andthe total cross sectional area of said ports being less than the crosssectional area of said outer gas discharge passage.

2, 9,663 1'5 16 3 1. The fuse assembly of claim. 29 wherein said tubesReferences Cited in the file of this'patent define outer and inner gasdischarge passages which are v individually and directly vented to theatmosphere ad- UNITED STATES PATENTS" jacent said other contact member.2:103:121 Slepian 1937 32. The fuse assembly of claim 31 wherein saidtubes 5 2,131,000 Petefmichl p 1933 are so dimensioned that each of saidgas discharge passages 2,152,497 Petel'michl 1939 has a progressivelyincreasing cross sectional area toward 2,250,211 Smith u 1941 its ventedend for facilitating expulsion of evolved gases.

33. The fuse assembly of claim 30 wherein said ports FOREIGN PATENTS areinclined toward the vented end of said outer passage 10 376,747 ItalyNov.*24, 1939 from the interior to the exterior of the inner tube.684,291 Germany i Nov. 25, 1939

